AITA for not asking my roommate to feed my cat?

Six years ago, my (29F) now husband/then boyfriend (29M) bought a condo in our city with his mom, each paying half of the down payment. She lives in a different state, so the condo is an investment property for her, but a live-in property for him. I have always lived in this condo with my husband since they bought it, and he, MIL, and I each pay 1/3 of the monthly mortgage.

Because my MIL pays 1/3 of the mortgage, her younger sons/my husband's brothers have each lived with us for a period of time, the idea being that their mom is covering their "rent" with her third of the mortgage. Currently, the youngest son of the family--Kevin (22M)--is living with us while he attends college in our city. In general, Kevin has been a good roommate in the two years he's lived here. He does his dishes and keeps his room clean, rarely has guests over (and if he does, they are very respectful), etc. My husband and I adopted a cat three years ago, before Kevin chose to go to college in our city and moved in with us. Kevin doesn't care much for animals, so he and the cat keep their distance from each other.

Here's the problem. In the past, when my husband and I have gone out of town for a few days, we've asked Kevin if he would mind feeding the cat. Kevin has a tendency to spontaneously leave town to visit friends, so his response is always that he doesn't know what his plans will be and he can't guarantee that he will be home and available to feed the cat. With that in mind, my husband and I have always asked other friends or hired pet-sitters to check in on the cat instead, understanding that it isn't Kevin's pet and he isn't obligated to care for him.

This summer, my husband and I are taking a two-week honeymoon trip. Kevin is currently on summer vacation from college, and knowing he enjoys his freedom, we assumed he wouldn't want to be responsible for the cat for two weeks. Instead, we asked MY brother Nathan (22M) to stay in our bedroom in the condo and take care of the cat for the two weeks we are away. Nathan is an animal-lover who often cares for others' pets when they're on vacation. Nathan lives in a small town with my mom, so he was excited to stay in our condo in the city for two weeks and take care of the cat. Unlike Kevin, who would plop food in the cat's bowl and call it a day, I know Nathan will feed him, give treats, scoop litter, let the cat sleep in his room, and give lots of pets and kisses. I thought this would be a win for everyone--Kevin gets his freedom to come and go as he pleases, Nathan gets to stay in the city in our empty room for two weeks, and my husband and I can have peace of mind knowing that Nathan would be taking excellent care of our pet.

Today, about a month before our honeymoon, my husband let Kevin know that Nathan would be coming to take care of the cat while we're away. To our surprise, he went off on my husband, saying how inconsiderate we are and how we should have asked him before arranging for someone else to stay in the condo. He feels that it will be awkward for him to share the space with Nathan, and he was looking forward to having the condo to himself for two weeks. To be fair, my husband works nights and I often work from home, so the condo is almost never empty. But Nathan is a respectful, introverted young man who I can't imagine will do anything to make his two week stay unpleasant for Kevin. And at the end of the day, we didn't think Kevin would be willing or able to provide consistent care for our cat.

Kevin called my MIL to get her involved, and she agrees with Kevin that my husband and I were inconsiderate to arrange for Nathan to stay without checking in with Kevin first. MIL also asserts that because she owns the condo too, she gets a say in what happens here. My husband, a people-pleaser, has apologized to Kevin and MIL and believes we should yield to them and tell Nathan not to come. I, on the other hand, know that our intention was to make Kevin's life easier and we made a choice that was consistent with his past behavior. I also want to ensure that my cat receives quality care and affection for two weeks. And at the end of the day, my husband and I pay 2/3 of the mortgage and I think we should be allowed to have a respectful guest stay in our bedroom.

So am I the asshole? Should I tell Nathan to stay home, knowing I will spend my two-week honeymoon stressed about whether my cat is okay?